Problem: $\dfrac{3}{4} - \dfrac{3}{8} = {?}$
Solution: $ = {\dfrac{3 \times 2}{4 \times 2}} - {\dfrac{3 \times 1}{8 \times 1}} $ $ = {\dfrac{6}{8}} - {\dfrac{3}{8}} $ $ = \dfrac{{6} - {3}}{8} $ $ = \dfrac{3}{8}$